Common skin disorders such as psoriasis, dermatitis, and eczema afflict large numbers of people each year. The prior art teaches a variety of medicinal and other lotions, creams, salves and ointments intended for external application to human skin and claimed to have a variety of beneficial properties ranging from merely moisturizing and cleansing to alleviating all manner of skin disorders. Exemplary of such prior art are U.S. Pat. Nos. 153,008; 1,525,285; and 3,016,334. None of these prior art compositions, however, has proved to be wholly satisfactory in treating skin disorders such as psoriasis, dermatitis and eczema. The Merck Index (7th ed. 1960) recognizes that coal tar in 3-5% ointment or 2% solution is useful in treating such diseases, but it cautions that prolonged skin contact can actually induce dermatitis and skin cancer. Topical corticosteroids have been used with varying success for treating psoriasis. With prolonged use under plastic occlusion they may result in atrophy of the skin.
Internal cytotoxic agents have also been used, but they have serious side-effects, including liver damage and bone marrow suppression.
Ultraviolet light is another useful method for treating psoriasis, and its effect can be increased by use of coal tar ointment or topical or internal psoralens. This approach usually requires repeated visits to the physician's office or an inpatient stay of several weeks. Thus, a safe and effective means for treating such skin lesions is still being sought.
Melanins are complex aggregate organic materials which are found naturally in skin, hair and eyes of mammals, in insect cuticle and in plants, or which may be produced synthetically from either dopa or quinone precursors as described in the Merck Index. A large variety of studies have been performed on the chemical nature and properties of melanins, two of the most complete and most recent reviews being Leon M. Edelstein, "Melanin: A Unique Biopolymer", in 1971 Pathobiology Annual 309-324 and Ralph D. Lillie, "Histochemistry of Melanins", in 1969 Pigments in Pathology 327-351, edited by M. Wolman. In general, melanins are best known for their skin and hair dyeing properties. For example, in U.S. Pat. No. 2,745,788, hydroquinone is oxidized to melanin and used to tint or dye hair. The therapeutic properties of melanins in treating skin diseases have not heretofore been recognized.